Engine lubricant compositions may be selected to provide an increased engine protection while providing an increase in fuel economy and reduced emissions. However, in order to achieve benefits of improved fuel economy and reduced emissions, a balance between engine protection and lubricating properties is required for the lubricant composition. For example, an increase in the amount of friction modifiers may be beneficial for fuel economy purposes but may lead to reduced ability of the lubricant composition to handle water. Likewise, an increase in the amount of anti-wear agent in the lubricant may provide improved engine protection against wear but may be detrimental to catalyst performance for reducing emissions.
The same is true for soot and sludge handling components of the lubricant composition. As the amount of dispersant in the lubricant composition is increased, typically, the soot and sludge handling properties of the lubricant are improved. However, increasing the amount of dispersant may adversely affect elastomeric seals since dispersants are typically aminic nitrogen containing-compounds that are detrimental to seals. It is believed that by introducing polyaromatic functionality into a dispersant improves the dispersant's ability to control soot related viscosity increase. Accordingly dispersants reacted with phthalic anhydride or naphthalic anhydride and capped with a cyclic carbonate are believed to provide better soot handling capabilities than conventional dispersants. However, such functionalized dispersants often exhibit poor elastomeric seal compatibility even at relatively low treat rates. Accordingly, there is a need for dispersants that can provide improved soot handling as well as improved seal compatibility and that are suitable for meeting or exceeding currently proposed and future lubricant performance standards.
With regard to the foregoing, embodiments of the disclosure provide an engine lubricant composition, a method for maintaining the soot handling capability of an engine lubricant while not adversely affecting elastomeric seal material in the engine and a method of operating an engine. The engine lubricant includes a base oil and a dispersant that is a reaction product of A) a hydrocarbyl-dicarboxylic acid or anhydride, B) a polyamine, C) a dicarboxyl-containing fused aromatic compound, and D) a non-aromatic dicarboxylic acid or anhydride.
Another embodiment of the disclosure provides a method for maintaining the soot handling capability of an engine lubricant for an engine without adversely affecting elastomeric seals in the engine. The method includes formulating a lubricant composition for the engine with a base oil and an additive that is a reaction product of A) a hydrocarbyl-dicarboxylic acid or anhydride, B) a polyamine, C) a dicarboxyl-containing fused aromatic compound, and D) a non-aromatic dicarboxylic acid or anhydride.
A further embodiment of the disclosure provides a method for operating an engine including formulating an engine lubricant for the engine having a base oil and a lubricant additive package containing a reaction product of A) a hydrocarbyl-dicarboxylic acid or anhydride, B) a polyamine, C) a dicarboxyl-containing fused aromatic compound, and D) a non-aromatic dicarboxylic acid or anhydride; and operating the engine with the engine lubricant.
An unexpected advantage of the use of the functionalized dispersant of the disclosed embodiments is that while the functionalized dispersant is suitable for handling soot, the functionalized dispersant has superior elastomeric seal protection properties. A further advantage of the use of the functionalized dispersant described herein is that a lower amount of functionalized dispersant may be used to achieve the soot handling capability compared to a conventional dispersant.
The following definitions of terms are provided in order to clarify the meanings of certain terms as used herein.
As used herein, the terms “oil composition,” “lubrication composition,” “lubricating oil composition,” “lubricating oil,” “lubricant composition,” “lubricating composition,” “fully formulated lubricant composition,” and “lubricant” are considered synonymous, fully interchangeable terminology referring to the finished lubrication product comprising a major amount of a base oil plus a minor amount of an additive composition.
As used herein, the terms “additive package,” “additive concentrate,” and “additive composition” are considered synonymous, fully interchangeable terminology referring the portion of the lubricating composition excluding the major amount of base oil stock mixture.
As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:                (1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form an alicyclic radical);        (2) substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);        (3) hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents such as pyridyl, furyl, thienyl, and imidazolyl. In general, no more than two, for example, no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.        
As used herein, the term “percent by weight”, unless expressly stated otherwise, means the percentage the recited component represents to the weight of the entire composition.
The terms “oil-soluble” or “dispersible” used herein may but do not necessarily indicate that the compounds or additives are soluble, dissolvable, miscible, or capable of being suspended in the oil in all proportions. The foregoing terms do mean, however, that they are, for instance, soluble or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is employed. Moreover, the additional incorporation of other additives may also permit incorporation of higher levels of a particular additive, if desired.
Lubricating oils, engine lubricating oils, and/or crankcase lubricating oils of the present disclosure may be formulated by the addition of one or more additives, as described in detail below, to an appropriate base oil formulation. The additives may be combined with a base oil in the form of an additive package (or concentrate) or, alternatively, may be combined individually with a base oil. The fully formulated lubricant, engine lubricant, and/or crankcase lubricant may exhibit improved performance properties, based on the additives added and their respective proportions.
Additional details and advantages of the disclosure will be set forth in part in the description which follows, and/or may be learned by practice of the disclosure. The details and advantages of the disclosure may be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.